Systems and methods for regulating temperature and illumination intensity at the distal tip of an endoscope

ABSTRACT

The present specification describes a system and method for computing the temperature of the tip of a multiple viewing elements endoscope based on a measurement of junction temperatures of light emitting diode (LED) illuminators inside the tip. The measurement of temperature is used for taking corrective action if the temperature exceeds a limit. The temperature measurement is used for optimizing image parameters, as the performance of image sensors is affected by changes in ambient temperature.

CROSS-REFERENCE

The present application relies on U.S. Patent Provisional ApplicationNo. 62/156,418, entitled “System and Method for Measurement ofTemperature at the Distal Tip of an Endoscope”, and filed on May 4,2015, for priority. The present application also relies on U.S. PatentProvisional Application No. 62/235,768, entitled “A Method of RegulatingIllumination for Multiple Viewing Element Endoscopes”, and filed on Oct.1, 2015, for priority. Both of the above-mentioned applications areherein incorporated by reference in their entirety.

The present application is also continuation-in-part of U.S. patentapplication Ser. No. 14/274,323 (the '323 application) entitled “AnEndoscope Tip Position Visual Indicator and Heat Management System”, andfiled on May 9, 2014, which, in turn, relies on U.S. Patent ProvisionalApplication No. 61/822,805, filed on May 13, 2013.

The '323 application is a continuation-in-part application of U.S.patent application Ser. No. 13/984,028, entitled “Multi-Element Coverfor a Multi-Camera Endoscope”, filed on Aug. 22, 2013 and issued as U.S.Pat. No. 9,101,266 on Aug. 11, 2015, which is a 371 National Stage Entryof PCT Application Number PCT/IL2012/050037, of the same title and filedon Feb. 6, 2012, which, in turn, relies upon U.S. Provisional PatentApplication No. 61/439,948, filed on Feb. 7, 2011, for priority, and isherein incorporated by reference.

The '323 application is also a continuation-in-part application of U.S.patent application Ser. No. 13/992,021, entitled “Fluid ChannelingComponent of a Multi-Camera Endoscope”, filed on Jun. 6, 2013 and issuedas U.S. Pat. No. 9,320,419 on Apr. 26, 2016, which is a 371 NationalStage Entry of PCT Application Number PCT/IL2011/050050, entitled“Flexible Electronic Circuit Board Multi-Camera Endoscope” and filed onDec. 8, 2011, which, in turn, relies upon U.S. Provisional PatentApplication No. 61/421,240, filed on Dec. 9, 2010, for priority, and isherein incorporated by reference.

The '323 application is also a continuation-in-part application of U.S.patent application Ser. No. 13/992,014, entitled “Flexible ElectronicCircuit Board for a Multi-Camera Endoscope” and filed on Jun. 6, 2013,which is a 371 National Stage Entry of PCT Application NumberPCT/IL2011/050049, of the same title and filed on Dec. 8, 2011, which,in turn, relies upon U.S. Provisional Patent Application No. 61/421,238,filed on Dec. 9, 2010, for priority, and is herein incorporated byreference.

The '323 application is also a continuation-in-part application of U.S.patent application Ser. No. 13/882,004, entitled “Optical Systems forMulti-Sensor Endoscopes” and filed on May 23, 2013, which is a 371National Stage Entry of PCT Application Number PCT/IL2011/000832, of thesame title and filed on Oct. 27, 2011, which, in turn, relies upon U.S.Provisional Patent Application No. 61/407,495, filed on Oct. 28, 2010,for priority, and is herein incorporated by reference.

The '323 application is also a continuation-in-part application of U.S.patent application Ser. No. 13/822,908, entitled “Multi-Camera EndoscopeHaving Fluid Channels” and filed on Mar. 13, 2013, which is a 371National Stage Entry of PCT Application Number PCT/IL2011/000745, of thesame title and filed on Sep. 20, 2011, which, in turn, relies upon U.S.Provisional Patent Application No. 61/384,354, filed on Sep. 20, 2010,for priority, and is herein incorporated by reference.

The '323 application is a continuation-in-part application of U.S.patent application Ser. No. 13/713,449, entitled “Removable TipEndoscope” and filed on Dec. 13, 2012, which, in turn, relies upon U.S.Provisional Patent Application No. 61/569,796, of the same title andfiled on Dec. 13, 2011, for priority, and is herein incorporated byreference.

The '323 application is also a continuation-in-part application of thefollowing United States Patent Applications, which are hereinincorporated by reference in their entirety:

U.S. patent application Ser. No. 13/655,120, entitled “Multi-CameraEndoscope” and filed on Oct. 18, 2012;

U.S. patent application Ser. No. 13/212,627, entitled “Multi-ViewingElement Endoscope” and filed on Aug. 18, 2011; and

U.S. patent application Ser. No. 13/190,968, entitled “Multi-CameraEndoscope”, filed on Jul. 26, 2011 and issued as U.S. Pat. No. 9,101,268on Aug. 11, 2015, all of which are continuation-in-part applications ofU.S. patent application Ser. No. 13/119,032, entitled “Multi-CameraEndoscope” and filed on Jul. 15, 2011, which is a 371 National StageEntry of PCT Application Number PCT/IL2010/000476, of the same title andfiled on Jun. 16, 2010, which, in turn, relies upon U.S. ProvisionalPatent Application No. 61/218,085 filed on Jun. 18, 2009, for priority.

The '323 application is also a continuation-in-part application of U.S.patent application Ser. No. 13/413,252, entitled “Multi Camera EndoscopeAssembly Having Multiple Working Channels”, filed on Mar. 6, 2012 andissued as U.S. Pat. No. 9,101,287 on Aug. 11, 2015, which, in turn,relies upon U.S. Provisional Patent Application No. 61/449,746, of thesame title and filed on Mar. 7, 2011, for priority, and is hereinincorporated by reference.

The '323 application is also a continuation-in-part application of U.S.patent application Ser. No. 13/413,141, entitled “Multi Camera EndoscopeHaving a Side Service Channel”, filed on Mar.6, 2012, and issued as U.S.Pat. No. 8,926,502 on Jan. 6, 2015, which, in turn, relies upon U.S.Provisional Patent Application No. 61/449,743, of the same title andfiled on Mar. 7, 2011, for priority, and is herein incorporated byreference.

The '323 application is also a continuation-in-part application of U.S.patent application Ser. No. 13/413,059, entitled “Endoscope CircuitBoard Assembly” and filed on Mar. 6, 2012, which, in turn, relies uponU.S. Provisional Patent Application No. 61/449,741, of the same titleand filed on Mar. 7, 2011, for priority, and is herein incorporated byreference.

The '323 application is also a continuation-in-part application of U.S.patent application Ser. No. 13/412,974, entitled “Camera Assembly forMedical Probes” and filed on Mar. 6, 2012, which, in turn, relies uponU.S. Provisional Patent Application No. 61/449,739, of the same titleand filed on Mar. 7, 2011, for priority, and is herein incorporated byreference.

The present application relates to U.S. patent application Ser. No.14/705,355, entitled “Systems and Methods of Distributing Illuminationfor Multiple Viewing Element and Multiple Illuminator Endoscopes” andfiled on May 6, 2015, which relies on, for priority, U.S. ProvisionalPatent Application No. 61/989,895, entitled “Multi-IlluminatorEndoscopic Lens Actuation Systems” and filed on May 7, 2014, which isherein incorporated by reference in its entirety.

The present application relates to U.S. patent application Ser. No.14/603,137, entitled “Image Capture and Video Processing Systems andMethods for Multiple Viewing Element Endoscopes”, filed on Jan. 22,2015, which relies on U.S. Provisional Patent Application No.61/930,101, entitled “Daisy Chain Multi-Sensor Endoscopic System” andfiled on Jan. 22, 2014 and U.S. Provisional Patent Application No.61/948,012, entitled “Parallel Illuminating Systems” and filed on Mar.4, 2014.

All of the above-mentioned applications are herein incorporated byreference in their entirety.

FIELD

The present specification relates generally to endoscopes with multipleviewing elements, and more specifically, to systems and methods forregulating the temperature at the distal tip of an endoscope and forregulating the illumination level of an endoscope based on an activitylevel.

BACKGROUND

Endoscopes have attained great acceptance within the medical communitysince they provide a means for performing procedures with minimalpatient trauma while enabling the physician to view the internal anatomyof the patient. Over the years, numerous endoscopes have been developedand categorized according to specific applications, such as, cystoscopy,colonoscopy, laparoscopy, and upper gastrointestinal endoscopy, amongothers. Endoscopes may be inserted into the body's natural orifices orthrough an incision in the skin.

An endoscope typically comprises an elongated tubular shaft, rigid orflexible, having a video camera or a fiber optic lens assembly at itsdistal end. The shaft is connected to a handle which sometimes includesan ocular for direct viewing. Viewing is also usually possible via anexternal screen. Various surgical tools may be inserted through aworking channel in the endoscope for performing different surgicalprocedures.

Endoscopes, such as colonoscopes and gastroscopes, that are currentlybeing used, typically have at least a front camera for viewing aninternal organ, such as, the colon, an illuminator for illuminating thefield of view of the camera, a fluid injector for cleaning the cameralens, and a working channel for insertion of surgical tools, forexample, tools for removing polyps found in the colon. Commonly usedilluminators comprise optical fibers which transmit light, generatedremotely, to the endoscope tip section. In more currently developedendoscopes, discrete illuminators such as light-emitting diodes (LEDs)have been incorporated for providing illumination.

Multiple viewing elements endoscopes comprise two or more sets ofoptical assemblies, each having an optical lens associated with an imagesensor and two or more illuminators. Other than flexible electronicboards, separate circuit boards are employed to hold and support theilluminators in a desired position with reference to the associatedoptical assemblies. The use of additional circuit boards increases thenumber of components that are required to be fitted into the limitedspace available in the tip of the endoscope. Since most of thecomponents dissipate some power in the form of heat, use of multiplesets of illuminators, sensors and viewing elements produces asignificant amount of heat in the distal tip during an endoscopicprocedure. Tip heating not only causes discomfort to the patient, butmay also affect performance of some of the electronic components insidethe tip. Failure of a component to operate due to too high a temperatureis also known. In some cases, the failure is reversible and vanishes astemperature drops again to normal levels, while in others it isirreversible. In particular, under high temperature conditions, LEDsexhibit reduced brightness and a shift in chromaticity towards blue. Ingeneral, imagers experience higher noise and a change in imagecharacteristics such as hue, saturation, brightness and contrast athigher temperatures. Hence, there is a need for a method and system tomeasure and regulate the temperature of the distal tip. Existing methodsof measuring the temperature at the distal tip involve the use of adedicated sensor and wiring, which occupy valuable space and add to thecrowding of components inside the tip.

Therefore, there is a need for methods and devices for measuring thetemperature of a distal tip which can advantageously use existingcomponents located within the tip of a multiple viewing elementsendoscope. Such a method should provide for dynamic measurement oftemperature, so that the temperature may be adjusted by reducing thepower of suitable components, thus avoiding overheating.

Conventional multiple viewing elements endoscopes typically comprisemultiple sets of illuminators that are operated in a very sub-optimalmanner. A multiple sensor or multiple viewing elements endoscope tipsection comprising a front-pointing camera and two or more side-pointingcameras positioned at or in proximity to a distal end of the tip sectionand a working channel configured for insertion of a surgical tool isdisclosed in U.S. patent application Ser. No. 13/655,120, entitled“Multi-Camera Endoscope” and filed on Oct. 18, 2012, assigned to theApplicant of the present specification and herein incorporated byreference in its entirety. As described in the '120 application, thefield of view (FOV) of each camera sensor in a multiple sensor endoscopeis illuminated by two or more illuminators that are light emittingdiodes (LEDs). Thus, multiple sensor endoscopes' tips that include aright pointing camera or viewing element, a front pointing camera orviewing element and a left pointing camera or viewing element mayinclude a minimum of six or more LEDs. In some embodiments, each viewingelement comprises three illuminators, totaling nine LEDs. Similarly,multiple sensor endoscope tip sections that include a front pointingcamera or viewing element and a side pointing camera or viewing elementmay include four, five or more LEDs.

Since the depth corresponding to the field of view of a camera can varysignificantly depending on the orientation of distal tip during acolonoscopy procedure (for example, when navigated through a patient'scolon), illuminating all LEDs with a fixed illumination intensity issub-optimal. Fixed illumination intensity may prove to be too weak insome orientations for example and may drive the camera sensor arraysbeyond their dazzle limits due to light reflection from a nearby wall inother orientations. In some cases, when driven beyond their dazzlelimits, camera sensor arrays such as Charge-Coupled Devices (CCDs) maycreate saturation and blooming that may appear as a white streak or blobin the generated images.

Further, keeping all LEDs illuminated at a constant intensity for longperiods of time may result in production of excessive heat at the tipsection of the endoscope. High temperature may adversely affect tissuesduring an endoscopic procedure. FIG. 1 shows a table 100 illustrating aquantitative relationship between temperature and thermal impact onporcine skin as published in “Studies of Thermal Injury: II. TheRelative Importance of Time and Surface Temperature in the Causation ofCutaneous Burns”, The American Journal of Pathology 23.5 (1947): 695 byMoritz, A. Re, and F. C. Henriques Jr. The table 100 providessub-threshold exposures 105 as well as threshold and supra-thresholdexposures 110 related to an increasing temperature 115 and time ofexposure 120. It is evident that severity of thermal injury to tissuesincreases with an increase in temperature and time of exposure.

One approach for controlling the illumination of a multiple illuminatorendoscope system may be provided by dynamically controlling the emittedlight or luminance intensities. It is further desirable to regulate theillumination of the multiple illuminators automatically in response tothe usage of the endoscope tip section.

Therefore, there is a need for systems and methods for automaticallydetecting the activity level corresponding to the tip section of anendoscope and responsively regulating the luminance intensity level ofeach illuminator associated with the tip section.

As such, it would also be highly advantageous to provide a method ofautomatically detecting if the endoscope tip section is stationary or inmotion and responsively regulating the luminance intensity level of eachilluminator independently.

SUMMARY

In some embodiments, the present specification discloses an endoscopysystem capable of measuring and regulating the temperature of its distaltip comprising: a plurality of viewing elements located in the endoscopetip, wherein each of said viewing elements comprises an image sensor anda lens assembly and is associated with one or more light emitting diode(LED) illuminators; a circuit board comprising a circuit for measuring avoltage across each of said LED illuminators; and a controllerprogrammed to compute a temperature of each of said LED illuminators byusing said measured voltage and a function representing a relationshipbetween LED voltage and LED junction temperature for a given current.

Optionally, the controller is further programmed to compute an averageof LED junction temperatures and use that average to compute thetemperature at a given point on the distal tip.

Optionally, the controller is further programmed to reduce a power ofthe LED illuminators if the average LED junction temperature exceeds apre-determined limit.

Optionally, the function representing the relationship between LEDvoltage and LED junction temperature is pre-determined by measuring LEDvoltage and LED junction temperature for a range of LED currents andidentifying a relationship between LED voltage and junction temperature.

Optionally, said function is separately estimated for each LEDilluminator present in each illuminator during an evaluation phase ofsaid endoscopy system. Still optionally, said function is estimatedusing regression analysis.

Optionally, a relationship between the average of LED junctiontemperatures and the temperature at a given point on the distal tip ispre-determined by measuring an average LED junction temperature and acorresponding temperature at a given point on the distal tip for a rangeof LED currents and identifying a relationship between average LEDjunction temperatures and temperatures for the given point on the distaltip. Still optionally, said relationship is estimated using regressionanalysis.

In some embodiments, the present specification discloses a method fordetermining a temperature in an endoscope, without using a separate,dedicated temperature sensor, wherein said endoscope comprises aplurality of viewing elements located in a distal tip of the endoscopeand wherein each of said viewing elements comprises an image sensor anda lens assembly and is associated with one or more LED illuminators,said method comprising: measuring a voltage across at least one of saidLED illuminators; and computing a junction temperature for the at leastone of said LED illuminators by using a value of the measured voltageand a function representing a relationship between LED voltage and LEDjunction temperature for a given current and for the at least one ofsaid LED illuminators.

Optionally, said method further comprises the step of computing anaverage of junction temperatures of at least two LED illuminatorspresent in the system and using that average to compute the temperatureat a given point on the distal tip.

Optionally, an average of junction temperatures of all the LEDilluminators is used to estimate the temperature at a given point on thedistal tip. Still optionally, an average of junction temperature of onlythe LED illuminators which are directly adjacent a given point on thedistal tip are used to estimate the temperature at said given point.

Optionally, a power of the at least one of said LED illuminator isreduced if a junction temperature of said LED illuminator exceeds apre-determined limit.

Optionally, the function representing the relationship between LEDvoltage and LED junction temperature is pre-determined by measuring LEDvoltage and LED junction temperature for a range of LED currents andidentifying a relationship between the LED voltage and LED junctiontemperature.

Optionally, a relationship between average LED junction temperature andthe temperature at a given point on the distal tip is pre-determined bymeasuring average LED junction temperature and the temperature at agiven point on the distal tip for a range of LED currents andidentifying a relationship between the average LED junction temperatureand the temperature at the given point.

In some embodiments, the present specification discloses a method ofregulating a luminance intensity of one or more illuminators of anendoscope tip section having a plurality of viewing elements, whereineach of the plurality of viewing elements is associated with at leastone of said one or more illuminators, the method comprising: obtaining afirst sample of images from each of the plurality of viewing elements ata first time instance, wherein each image of the first sample is dividedinto a plurality of blocks; obtaining a second sample of images fromeach of the plurality of viewing elements at a second time instance,wherein each image of the second sample is divided into a plurality ofblocks; calculating an average luminance for each block of the firstsample and for each block of the second sample; for each block,computing a change in the average luminance between the first sample andsecond sample; identifying blocks having a maximum average luminancechange among images of the first sample and the second sample;calculating a fraction of a total number of blocks whose maximum averageluminance change exceeds a first threshold value; and depending uponwhether said fraction of to the total number blocks does or does notexceed a second threshold value, performing one of the following steps:changing the luminance intensity of the at least one of said one or moreilluminators from a first intensity level to a second intensity level;changing the luminance intensity of the at least one of said one or moreilluminators from the second intensity level to the first intensitylevel; or, maintaining a luminance intensity of the at least one of saidone or more illuminators at the first intensity level or the secondintensity level.

Optionally, said first intensity level is higher than the secondintensity level.

Optionally, if said fraction of the total number of blocks exceed thesecond threshold value and the luminance intensity of the at least oneof said one or more illuminators is at a second intensity level, saidluminance intensity is changed from said second intensity level to saidfirst intensity level.

Optionally, if said fraction of the total number of blocks is lower thansaid second threshold value and the luminance intensity of the at leastone of said one or more illuminators is at a first intensity level, saidluminance intensity is changed from said first intensity level to saidsecond intensity level.

Optionally, said first intensity level ranges from 20 mA to 100 mA.

Optionally, said first intensity level corresponds to an active state ofthe at least one of said one or more illuminators.

Optionally, the change of the luminance intensity of the at least one ofsaid one or more illuminators to the first intensity level is indicativeof a motion of the distal tip section relative to its surroundings.

Optionally, the change of the luminance intensity of the at least one ofsaid one or more illuminators to the first intensity level is indicativeof at least one external object being brought within a predefineddistance from the distal tip section. Optionally, the predefineddistance is less than or equal to 5 centimeters from the distal tipsection.

Optionally, the second intensity level corresponds to a passive state ofthe at least one of said one or more illuminators.

Optionally, the change of the luminance intensity of the at least one ofsaid one or more illuminators from the first intensity level to thesecond intensity level is indicative of the distal tip section beingstationary relative to its surroundings.

Optionally, said first and second time instances differ by 0.5 seconds.

Optionally, said first and second thresholds are derived by computing aluminance histogram for the first sample and the second sample.

In some embodiments, the present specification discloses an endoscopetip section having a plurality of viewing elements and a processor,wherein each of the plurality of viewing elements has one or moreilluminators associated therewith and the processor is configured toregulate luminance intensity of at least one illuminator by: obtaining afirst sample of images from each of the plurality of viewing elements ata first time instance, wherein each image of the first sample is dividedinto a plurality of blocks; obtaining a second sample of images fromeach of the plurality of viewing elements at a second time instance,wherein each image of the second sample is divided into a plurality ofblocks; calculating an average luminance for each block of the first andsecond sample of images; for each block, computing an absolute value ofaverage luminance change between the first and second sample of images;identifying blocks having maximum absolute average luminance changeamong images corresponding to the plurality of viewing elements;calculating a fraction of the total number of blocks whose maximumaverage luminance change exceeds a first threshold value; and dependingupon whether said fraction of blocks does or does not exceed a secondthreshold value performing one of the following steps: changing theluminance intensity of said at least one illuminator from a firstintensity level to a second intensity level; changing the luminanceintensity of said at least one illuminator from a second intensity levelto a first intensity level; or, maintaining the luminance intensity ofsaid at least one illuminator at the first or second intensity level.

In some embodiments, the present specification discloses an endoscopetip section having a plurality of viewing elements and a processor,wherein each of the plurality of viewing elements has one or moreilluminators associated therewith and the processor is configured toregulate luminance intensity of at least one illuminator by detectingwhether said endoscope tip section is in an active state or a passivestate.

Optionally, the process of detecting whether said endoscope tip sectionis in an active state or a passive state comprises: obtaining a firstsample of images from each of the plurality of viewing elements at afirst time instance, wherein each image of the first sample is dividedinto a plurality of blocks; obtaining a second sample of images fromeach of the plurality of viewing elements at a second time instance,wherein each image of the second sample is divided into a plurality ofblocks; calculating an average luminance for each block of the first andsecond sample of images; for each block, computing an absolute value ofaverage luminance change between the first and second sample of images;identifying blocks having maximum absolute average luminance changeamong images corresponding to the plurality of viewing elements; and,calculating a fraction of the total number of blocks whose maximumaverage luminance change exceeds a first threshold value.

Optionally, depending upon whether said fraction of total number ofblocks does or does not exceed a second threshold value the process mayinclude performing one of the following steps: changing the luminanceintensity of said at least one illuminator from a first intensity levelto a second intensity level; changing the luminance intensity of said atleast one illuminator from a second intensity level to a first intensitylevel; or, maintaining the luminance intensity of said at least oneilluminator at the first or second intensity level.

In some embodiments, the present specification discloses a method ofregulating luminance intensity of at least one illuminator of anendoscope tip section having a plurality of viewing elements, whereineach of the plurality of viewing elements is with associated one or moreilluminators, the method comprising: obtaining a first sample of imagesfrom each of the plurality of viewing elements at a first time instance,wherein each image of the first sample is divided into a plurality ofblocks; obtaining a second sample of images from each of the pluralityof viewing elements at a second time instance, wherein each image of thesecond sample is divided into a plurality of blocks; calculating anaverage luminance for each block of the first and second sample ofimages; for each block, computing an absolute value of average luminancechange between the first and second sample of images; identifying blockshaving maximum absolute average luminance change among imagescorresponding to the plurality of viewing elements; and, calculating afraction of the total number of blocks whose maximum average luminancechange exceeds a first threshold value.

Optionally, depending upon whether said fraction of the total number ofblocks does or does not exceed a second value threshold the method mayinclude performing one of the following steps: changing the luminanceintensity of said at least one illuminator from a first intensity levelto a second intensity level; changing the luminance intensity of said atleast one illuminator from a second intensity level to a first intensitylevel; or, maintaining the luminance intensity of said at least oneilluminator at the first or second intensity level.

The aforementioned and other embodiments of the present specificationshall be described in greater depth in the drawings and detaileddescription provided below.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other features and advantages of the present specificationwill be appreciated, as they become better understood by reference tothe following detailed description when considered in connection withthe accompanying drawings, wherein:

FIG. 1 is a table illustrating time-surface temperature thresholds forthermal injury of porcine skin;

FIG. 2A illustrates an exemplary multiple viewing elements endoscopysystem, as used in an embodiment of the present specification;

FIG. 2B illustrates an isometric, external view of an endoscope havingmultiple viewing elements in which the systems and methods described inthe present specification may be implemented;

FIG. 2C illustrates an endoscope tip comprising multiple viewingelements and illuminators associated with such viewing elements in anendoscopy system in which the systems and methods described in thepresent specification may be implemented;

FIG. 3 illustrates a cross-sectional view of a tip section of amulti-camera endoscope, according to some embodiments;

FIG. 4 illustrates an exemplary temperature-voltage curve for an LED;

FIG. 5 illustrates an exemplary voltage-current curve for an LED;

FIG. 6 illustrates an electrical circuit for measuring the temperatureof a plurality of LED illuminators located in a distal tip section of anendoscope, in accordance with an embodiment of the presentspecification;

FIG. 7 illustrates a graph showing voltage-temperature curves forvarious forward currents for an exemplary LED;

FIG. 8 is a flowchart illustrating an exemplary evaluation process andtemperature-voltage function computation for a given LED, according toan embodiment of the present specification;

FIG. 9 is a flowchart illustrating an exemplary evaluation process for agiven model of an endoscope, according to an embodiment of the presentspecification;

FIG. 10 is a flowchart illustrating the process of temperaturedetermination during a real-time procedure, according to an embodimentof the present specification;

FIG. 11 depicts a block diagram of the control hardware for a multipleviewing elements endoscopy system, according to an embodiment of thepresent specification;

FIG. 12A is a graph illustrating the effect of ambient temperature onthe chromaticity coordinate; and

FIG. 12B is a graph illustrating the effect of ambient temperature onluminous flux.

FIG. 13A is a flow chart illustrating a plurality of steps of a methodof regulating illumination intensities of one or more illuminators of anendoscope tip section, according to certain embodiments of the presentspecification;

FIG. 13B is a flow chart illustrating a plurality of outcomes withreference to a decision step of the method of FIG. 13A, according tocertain embodiments of the present specification;

FIG. 14 is a block diagram illustrating an illuminator circuit,according to some embodiments;

FIG. 15A is a parallel illuminating system circuit diagram, according tosome embodiments;

FIG. 15B illustrates the parallel illuminating system circuit diagram ofFIG. 15A further incorporating a remote sense, according to someembodiments;

FIG. 16 is a block diagram illustrating another illuminator circuit,according to some embodiments; and

FIG. 17 is a block diagram illustrating yet another illuminator circuit,according to some embodiments.

DETAILED DESCRIPTION

In embodiments, the present specification discloses systems and methodsfor regulating the temperature at the distal tip of an endoscope andsystems and methods for regulating the illumination intensity of anendoscope based on an activity level. Individually or discretelyregulating the illumination intensity of each illuminator reduces theoverall power consumption of the endoscope and thus reduces heatproduction in the endoscope's tip section.

In an embodiment, the present specification discloses a system andmethod for measuring and regulating the temperature at the distal tip ofan endoscope. In some embodiments, the present specification discloses asystem and method for determining the temperature of the tip of amultiple viewing elements endoscope, without making use of a dedicatedtemperature sensor and/or associated circuitry which would occupyadditional space in the tip section. In an embodiment, temperaturedetermination is based upon measurement of at least one junctiontemperature of LED illuminators positioned within the tip section.Optionally, the temperature measurement is used for taking correctiveactions if the temperature reading and/or calculation does not fallwithin a pre-determined range, such as if the temperature exceeds apre-determined threshold limit. Optionally, a temperature measurement isused for optimizing image sensor parameters, since the performance ofimage sensors is affected by changes in ambient temperature.

In accordance with an embodiment, the present specification alsodiscloses a system and method for regulating the illumination intensityof each illuminator independently in a multiple viewing elementsendoscope. In embodiments of the present specification, the systemdynamically controls the illumination intensity of specific illuminatordevices and ensures that each device is operated in the most optimalmanner depending on the activity level and orientation of the distaltip.

In conventional endoscopes, fixed illumination intensity may prove to beweak in certain directions and may drive the camera sensor arrays beyondtheir dazzle limits due to light reflection from a nearby wall in otherdirections. In such circumstances, if the illumination intensity of allthe illuminator devices is increased or decreased together, it may solvethe problem in one direction but may further aggravate the problem inother directions. For example, reducing the illumination intensity mayprevent dazzle in the direction in which the intensity was high but itmay deteriorate the image quality in the direction in which theillumination intensity was already weak.

Another advantage of regulating each illuminator's illuminationintensity independently is that the different types of illuminators maybe switched between on and off states on demand or, in the alternative,may be set at a first intensity level, second intensity level and/or nthintensity level. For example, in an embodiment, the illuminators arespecific blue and green wavelength range LEDs implementing a narrow bandimaging technique, wherein the light of the specific blue and greenwavelengths is used to enhance the detail of certain aspects of thesurface of a mucosa, when needed.

In an embodiment, a processor of a main control unit, associated withthe multiple viewing elements endoscope, is configured to vary theillumination intensity of each illuminator automatically using an imageprocessing software program code.

The present specification is directed towards multiple embodiments. Thefollowing disclosure is provided in order to enable a person havingordinary skill in the art to practice the invention. Language used inthis specification should not be interpreted as a general disavowal ofany one specific embodiment or used to limit the claims beyond themeaning of the terms used therein. The general principles defined hereinmay be applied to other embodiments and applications without departingfrom the spirit and scope of the invention. Also, the terminology andphraseology used is for the purpose of describing exemplary embodimentsand should not be considered limiting. Thus, the present invention is tobe accorded the widest scope encompassing numerous alternatives,modifications and equivalents consistent with the principles andfeatures disclosed. For purpose of clarity, details relating totechnical material that is known in the technical fields related to theinvention have not been described in detail so as not to unnecessarilyobscure the present invention.

It should be noted herein that any feature or component described inassociation with a specific embodiment may be used and implemented withany other embodiment unless clearly indicated otherwise.

It is noted that the term “endoscope” as mentioned herein may referparticularly to a colonoscope and a gastroscope, according to someembodiments, but is not limited only to colonoscopies and/orgastroscopies. The term “endoscope” may refer to any instrument used toexamine the interior of a hollow organ or cavity of the body.

Further, the systems and methods of the present specification may beimplemented with any endoscope. An exemplary system is described inco-pending U.S. patent application Ser. No. 14/469,481, entitled“Circuit Board Assembly of A Multiple Viewing Elements Endoscope”, filedon Aug. 26, 2014 and herein incorporated by reference in its entirety.

Reference is now made to FIG. 2A, which shows a multi-viewing elementsendoscopy system 200. System 200 may include a multi-viewing elementsendoscope 202. Multi-viewing elements endoscope 202 may include a handle204, from which an elongated shaft 206 emerges. Elongated shaft 206terminates with a tip section 208 which is turnable by way of a bendingsection 210. Handle 204 may be used for maneuvering elongated shaft 206within a body cavity. The handle may include one or more buttons and/orknobs and/or switches 205 which control bending section 210 as well asfunctions such as fluid injection and suction. Handle 204 may furtherinclude at least one, and in some embodiments, one or more workingchannel openings 212 through which surgical tools may be inserted. Inembodiments, the handle 204 also includes one and more sideservice/working channel openings.

Tip 208 may include multi-viewing elements. In accordance with anembodiment, tip 208 includes a front viewing element and one or moreside viewing elements. In another embodiment, tip 208 may include only afront viewing element.

In addition, tip 208 may include one or more service/working channelexit point. In accordance with an embodiment, tip 208 includes a frontservice/working channel exit point and at least one side service channelexit point. In another embodiment, tip 208 may include two frontservice/working channel exit points.

A utility cable 214, also referred to as an umbilical tube, may connectbetween handle 204 and a Main Control Unit (MCU) 216. Utility cable 214may include therein one or more fluid channels and one or moreelectrical channels. The electrical channel(s) may include at least onedata cable for receiving video signals from the front and side-pointingviewing elements, as well as at least one power cable for providingelectrical power to the viewing elements and to the discreteilluminators.

The main control unit 216 contains the controls required for displayingthe images of internal organs captured by the endoscope 202. The maincontrol unit 216 may govern power transmission to the endoscope's 202tip section 208, such as for the tip section's viewing elements andilluminators. The main control unit 216 may further control one or morefluid, liquid and/or suction pump(s) which supply correspondingfunctionalities to the endoscope 202.

One or more input devices 218, such as a keyboard, a touch screen andthe like may be connected to the main control unit 216 for the purposeof human interaction with the main control unit 216.

In the embodiment shown in FIG. 2A, the main control unit 216 comprisesa screen/display 220 for displaying operation information concerning anendoscopy procedure when the endoscope 202 is in use. The screen 220 maybe configured to display images and/or video streams received from theviewing elements of the multi-viewing element endoscope 202. The screen220 may further be operative to display a user interface for allowing ahuman operator to set various features of the endoscopy system.

Optionally, the video streams received from the different viewingelements of the multi-viewing element endoscope 202 may be displayedseparately on at least one monitor (not seen) by uploading informationfrom the main control unit 216, either side-by-side or interchangeably(namely, the operator may switch between views from the differentviewing elements manually). Alternatively, these video streams may beprocessed by the main control unit 216 to combine them into a single,panoramic video frame, based on an overlap between fields of view of theviewing elements. In an embodiment, two or more displays may beconnected to the main control unit 216, each for displaying a videostream from a different viewing element of the multi-viewing elementendoscope 202. The main control unit 216 is described in U.S. patentapplication Ser. No. 14/263,896, entitled “Video Processing in a CompactMulti-Viewing Element Endoscope System” and filed on Apr. 28, 2014,which is herein incorporated by reference in its entirety.

FIG. 2B is an isometric, external view of an endoscope having multipleviewing elements. Referring to FIG. 2B, tip or head 230 of endoscope 200comprises at least a front pointing viewing element 236 and at least oneside pointing viewing element 256. The viewing elements may be an imagesensor, such as Charge Coupled Device (CCD) or a Complementary MetalOxide Semiconductor (CMOS) imager. Further, the term “viewing element”may generally refer to an image sensor and the optical system/assemblyrelated to the image sensor.

In an embodiment, the front viewing element 236 is located on the frontface 320 of head 230. In an embodiment, the optical axis of the frontviewing element is substantially directed along the long dimension ofthe endoscope. However, since the front viewing element typically has awide angle, its Field of View (FOV) may include viewing directions atlarge angles relative to its optical axis. Additionally, optical windows242 a and 242 b, which have discrete light sources such as LightEmitting Diodes (LEDs), are also seen on front face 320 of head 230. Itshould be noted that the number of LEDs used for illumination of the FOVmay vary. Further, the LEDs used may be white light LEDs, infrared lightLEDs, near infrared light LEDs, ultraviolet light LEDs or any other typeof LED.

In an embodiment, distal opening 340 of working channel 262 is locatedon front face 320 of head 230, such that a surgical tool insertedthrough working channel 262 and deployed beyond front face 320 may beviewed by the front viewing element 236. Distal opening 344 of a fluidchannel may preferably also be located on front face 320 of head 230.The fluid channel leading to distal opening 344 may be used as a jetchannel for cleaning the colon.

Liquid injector 346 having a nozzle 348 aimed at front viewing element236 is used for injecting fluid to wash contaminants such as blood,feces and other debris from front viewing element 236. Optionally, thesame injector is used for cleaning both front viewing element 236 andone or both optical windows 242 a and 242 b. Injector 346 may receivefluid (for example, water and/or gas) from the fluid channel or may befed by a dedicated cleaning fluid channel.

Visible on the side wall 362 of head 230 is the side pointing viewingelement 256 and optical window 252 having a discrete light source suchas LED. It may be noted that the number of the discrete light sourcesmay vary. In one embodiment, optical axis of side pointing viewingelement 256 may be substantially directed perpendicular to the longdimension of the endoscope. However, since side viewing elementtypically has a wide angle, its field of view may include viewingdirections at large angles to its optical axis.

Liquid injector 366 having a nozzle 368 aimed at side viewing element256 is used for injecting fluid to wash contaminants such as blood,feces and other debris from the side viewing element 256. Optionally,the same injector is used for cleaning both the side viewing element 256and optical window 252. Preferably, injectors 346 and 366 are fed fromsame channel. An optional groove 370 helps direct the cleaning fluidfrom nozzle 368 towards side viewing element 256.

In the depicted embodiment, flexible shaft 260 is constructed of aplurality of links 382 connected to each other by pivots 384. Links 382allows pushing, pulling and rotating the endoscope while pivots 384provide limited flexibility. Not seen in this figure are the electricalcables supplying power to the LEDs.

It should be noted that while only one side pointing viewing element isseen in FIG. 2B, optionally, according to some embodiments, two or moreside pointing viewing elements may be located within head 230. When twoside pointing viewing elements are used, they are preferably installedsuch that their field of views are substantially opposing. According tosome embodiments, different configurations and number of side pointingviewing elements are possible and covered within the general scope ofthe current specification.

Reference is now made to FIG. 2C, which illustrates another embodimentof an exemplary multiple viewing elements endoscope tip section 230comprising a plurality of viewing elements, also referred to as camerasor sensors, and an illuminating system comprising a plurality ofilluminators wherein at least one illuminator is associated with each ofthe plurality of viewing elements, according to certain embodiments. Theendoscope tip section 230 includes a front pointing viewing element 236,a first side pointing viewing element 256 and a second side pointingviewing element 276.

In accordance with an embodiment, the first side pointing viewingelement 256 has two associated side pointing illuminators 252 a and 252b illuminating an upper right field of view (FOV) 221 and a lower rightFOV 223 (the FOVs 221 and 223 may partially overlap in variousembodiments) to together illuminate a right FOV 280; the second sidepointing viewing element 276 has two associated side pointingilluminators 272 a and 272 b, which respectively illuminate a lower leftFOV portion 227 and an upper left FOV portion 228, together illuminatinga left FOV 285; and the front pointing viewing element 236 has threeassociated front pointing illuminators 242 a, 242 b and 242 c (the FOVsof the three front pointing illuminators may partially overlap invarious embodiments), which together illuminate a front FOV 290. Personsof ordinary skill in the art should appreciate that the number ofviewing elements and the number of illuminators associated with each ofthe viewing elements may vary in alternate embodiments. For example, anembodiment may comprise a front pointing viewing element and a sidepointing viewing element wherein each of the front and side pointingviewing elements may have one, two or more illuminators associated withthem. In accordance with various embodiments the viewing elements orcameras 236, 256 and 276 are associated with Charge-Coupled Device (CCD)or Complementary Metal Oxide Semiconductor (CMOS) image sensor arrays.Also, front illuminators 242 a, 242 b and 242 c and side illuminators252 a, 252 b, 272 a, 272 b are, in an embodiment, discrete illuminatorsand include a light-emitting diode (LED), which may be a white lightLED, an infrared light LED, a near infrared light LED, an ultravioletlight LED or any other LED. In an embodiment, each illuminator includesone, two or more LED. In various embodiments, all the illuminatorsinclude the same type of one or more LEDs (white, infrared, nearinfrared, ultraviolet, etc.) or a combination of the different types ofone or more LEDs. The term “discrete”, concerning discrete illuminator,refers to an illumination source, which generates light locally andinternally, in contrast to a non-discrete illuminator, which may be, forexample, a fiber optic merely transmitting light generated remotely.

In accordance with an embodiment, each of the first side pointingilluminators 252 a, 252 b include a single LED that are seriallyconnected to each other and each of the second side pointingilluminators 272 a, 272 b include a single LED that are also seriallyconnected to each other. In one embodiment, each of the front pointingilluminators 242 a, 242 b, 242 c includes a single LED and the threeLEDs (corresponding to the illuminators 242 a, 242 b, and 242c) areconnected serially to each other. In another embodiment, each of thefront pointing illuminators 242 a, 242 b, 242 c includes two LEDs(forming three pairs of LEDs) that are connected in parallel to eachother within their corresponding illuminators 242 a, 242 b, 242c;however the three illuminators 242 a, 242 b, 242 c (including the threepairs of LEDs)connect to each other serially.

It should be understood that the endoscope tip section 230 includes aworking channel, a fluid injector channel, a jet channel having anopening positioned on the front face 320 that is configured to insertsurgical tools and to inject fluids or gases, a flexible electroniccircuit board configured to carry the front and side viewing elementsalong with the associated illuminators and objective lens systems, thewiring connections between these components and a cable connecting theendoscopic tip 230 to an endoscope handle which in turn is coupled to anexternal main control unit and a display.

Reference is now made to FIG. 3, which shows a cross-sectional view of atip section 300 of a multiple viewing elements endoscope, according toan embodiment. In an embodiment, the tip section 300 includes afront-pointing image sensor 302, such as a Charge Coupled Device (CCD)or a Complementary Metal Oxide Semiconductor (CMOS) image sensor. In anembodiment, the front-pointing image sensor 302 is mounted on anintegrated circuit board 306, which may be rigid or flexible indifferent embodiments. In an embodiment, the integrated circuit board306 supplies front-pointing image sensor 302 with the necessaryelectrical power and derives still images and/or video feeds captured bythe image sensor. In an embodiment, the integrated circuit board 306 isconnected to a set of electrical cables (not shown) which in anembodiment are threaded through an electrical channel running throughthe elongated shaft of the endoscope. In embodiments, the front-pointingimage sensor 302 is coupled to a lens assembly 304 which is mounted ontop of it and provides the necessary optics for receiving images. Inembodiments, the lens assembly 304 includes a plurality of lenses,static or movable, which may provide a field of view of at least 90degrees and up to essentially 180 degrees. In an embodiment, lensassembly comprises fisheye lenses. Front-pointing image sensor 302 andlens assembly 304, with or without integrated circuit board 306, may bejointly referred to as a “front pointing viewing element”.

In embodiments, one or more discrete front illuminators 308, such asLEDs, are placed next to lens assembly 304, for illuminating its fieldof view. Optionally, discrete front illuminators 308 are attached to thesame integrated circuit board 306 on which front-pointing image sensor302 is mounted (this configuration is not shown).

In an embodiment, the tip section 300 further includes a side-pointingimage sensor 312, such as a Charge Coupled Device (CCD) or aComplementary Metal Oxide Semiconductor (CMOS) image sensor. In anembodiment, the side-pointing image sensor 312 is mounted on anintegrated circuit board 316, which may be rigid or flexible indifferent embodiments. In an embodiment, the integrated circuit board316 supplies side-pointing image sensor 312 with the necessaryelectrical power and derives still images and/or video feeds captured bythe image sensor. In an embodiment, the side-pointing image sensor 312is coupled to a lens assembly 314 which is mounted on top of it andprovides the necessary optics for receiving images. Side-pointing imagesensor 312 and lens assembly 314, with or without integrated circuitboard 316, may be jointly referred to as a “side pointing viewingelement”.

In embodiments, one or more discrete side illuminators 318, such asLEDs, are placed next to lens assembly 314, for illuminating its fieldof view. Optionally, discrete front illuminators 318 are attached to thesame integrated circuit board 316 on which side-pointing image sensor312 is mounted (this configuration is not shown).

In another configuration, integrated circuit boards 306 and 316 comprisea single integrated circuit board on which both front and side-pointingimage sensors 302 and 312 are mounted. In embodiments, the front andside-pointing image sensors 302 and 312 may be similar or identical interms of, for example, field of view, resolution, light sensitivity,pixel size, focal length, focal distance and/or the like. Further, theremay be two side-pointing image sensors, as described above.

One of ordinary skill in the art would appreciate that having multiplecameras and LED-based illuminants in the tip increases heat dissipation.During an endoscopy procedure, the distal tip's temperature is usuallymoderated by the heat dissipating properties of the patient, the gasflow, and the water jets. However, it is desirable to provide a dynamicregulation of temperature in the distal tip in order to lower the stresson the electronic components, thereby improving both performance andmean time between failures (MTBF). A device with a higher MTBF hashigher reliability. Further, an increase in the number of componentsnecessarily implies that more components are required to be tested inBIT (Built-In Test). Conventional systems cannot identify LEDmalfunctions and failures in the distal tip, such as short or opencircuits or unassembled LEDs since LED voltages are not measured.

The present specification achieves the dual purpose of temperaturemeasurement and functional testing at the distal tip by using thevoltage-current dependency of the illuminators (LEDs) themselves. Themethods of the present specification takes advantage of the premise thatfor any given current (forward current, If), an LED's voltage (forwardvoltage, Vf) drops as its junction temperature rises. This behaviorapplies to all LEDs at any forward current. Hence, an LED can be used asa temperature sensor once its forward current is known. The presentmethods therefore, enable measurement of temperature at the distal tipwithout using dedicated temperature sensors and wiring. This conservesvaluable space in the distal tip and also provides a means for immediatedetection of any LED malfunction in the tip.

FIG. 4 illustrates an exemplary temperature-voltage curve for an LED ata forward current (I_(FP)) of 80 mA. Referring to FIG. 4, as the ambienttemperature Ta 401 rises, there is a corresponding decrease in the LEDforward voltage Vf 402. It is seen that the typical slope of aTemperature-Voltage curve is −1 mV/° C.˜−3 mV/° C., and varies with theforward current (If).

FIG. 5 illustrates another curve showing the relationship betweenforward voltage Vf and forward current If, for a given ambienttemperature Ta. Referring to FIG. 5, for a given ambient temperature of25° C., forward voltage Vf 501 increases as forward current If 502increases.

The methods of the present specification compute the mathematicalrelationship between the following variables: forward voltage Vf,forward current If, and ambient temperature Ta, to dynamically determinethe junction temperature of an LED. Further, in an embodiment, themethods of the present specification determine the temperature of atleast two, or all, of the LEDs in the distal tip and compute an averagetemperature to compensate for any errors in measurement which may arisedue to using the LED as a temperature sensor.

FIG. 6 illustrates an electrical circuit 600 for measuring thetemperature of a chain of LED illuminators 601 located in the distal tip650 of an endoscope. In an embodiment, the circuit is located on thecamera board (CB) 660, which is a part of the controller (MCU) (216 inFIG. 2A) of the endoscope. In an embodiment, the main connector board(MCB) 670 is a miniature unit located in a proximal end of the endoscopeitself and supports two main tasks requiring non-volatile memory(EEPROM) and a parallel-I2C I/O expander.

It may be noted that an endoscope with multiple viewing elementstypically has at least a corresponding number of illuminators. Forexample, an endoscope with three cameras may have three chains of LEDs,each chain composed of several LEDs connected in series. In anembodiment, each chain of LEDs is in electrical communication withelectrical circuit 600.

Referring to FIG. 6, the circuit comprises a first high precision, highvoltage op-amp (operational amplifier) 602 in a voltage-followerconfiguration that buffers the voltage of the LED-chain and drives theresistive ladders 603 without drawing significant current from the chain601. In an embodiment, the set of resistive ladders 603 comprises fourresistive ladders, each being fed by the op-amp 602. In an embodiment,gains of the four resistive ladders are 1, ½, ⅓ and ¼, respectively andare designed to normalize the input of ADC (Analog to Digital Converter)604 to be equivalent to that of a single LED in the chain of LEDs. In anembodiment, the input of ADC 604 is equivalent to that of a single LED,regardless of the number of LEDs in the chain. This ensures that theADC's input does not exceed a permitted upper limit if a chain has morethan one LED.

In an embodiment, the circuit further comprises a set of three accuratereference voltages 605. Exemplary values of reference voltages are 10mV, 3.2V, and 4.096V, with an accuracy of at least 0.02%. In anembodiment, all reference voltages stem from a single source. In anembodiment, an analog multiplexer 606 is provided for selecting one ofthe resistive ladders and one of the reference voltages (10 mV or 3.2V)that feed the ADC 604, via second op-amp 607. In an embodiment, theabove selection is made on the basis of the number of LEDs in series perchain. In an embodiment, this number is extracted from identificationdata stored in the EEPROM 609 of the MCB 670. In various embodiments,the chosen ladder as a function of LEDs in a chain is: 1 LED:1; 2 LEDs:½; 3 LEDs: ⅓; and 4 LEDs: ¼. The third reference voltage (which is4.096V as mentioned above) acts as the reference voltage for the ADC604, which measures the voltage over the chain of LEDs 601. In anembodiment, ADC resolution is at least 16-bits, with zero-scale andfull-scale errors each being of the order of lmV or better.

In an embodiment, N-Ch MOSFETS (not shown) are provided at the base ofeach resistive ladder, which switch on only the resistive ladder in use,thereby reducing op-amp load and heat dissipation. In an embodiment,resistors composing the resistive ladders are encapsulated inmulti-resistor array modules to achieve highest precision(resistor-resistor tracking precision).

It may be noted that while the electrical circuit 600 for temperaturemeasurement is in electrical communication with each chain of LEDs, someof the components may be used to serve more than one chain. For example,in an embodiment, a multi-channel ADC instead of a single channel ADC isused. Similarly, in embodiments, the control component 608 and EEPROM609 are commonly employed for all chains. In an embodiment, EEPROM 609,or any other type of non-volatile memory installed in the endoscope'sMCB (Main Connector Board) 670 is used for storing LED parameters andpolynomials representing voltage-temperature relationship for differenttypes of LEDs. This data is used for temperature measurement at the LEDjunctions. In an embodiment, the current source 610 is unique for everychain of LEDs. In various embodiments, the resistive ladders 603, analogto digital converter (ADC) 604, reference voltages 605, analogmultiplexer 606, and second op-amp 607 are unique per chain. Anadvantage of having unique components for each chain is simultaneousreading of all chains resulting in better accuracy and reading speed. Adisadvantage is the requirement for additional hardware, as each of saidcomponents is duplicated for each chain. In other embodiments, thesecomponents are shared by all chains. When the components are all shared,a first op-amp 602 must be proceeded by an analog multiplexer (notshown) to select which chain voltage should drive it at any given pointin time. Whether or not components 603 through 607 are unique or shared,control component 608 is preferably shared by all chains, regardless ofthe number of chains, since there is only one inter-integrated circuit(I2C) bus connecting the EEPROM 609 with said control component 608 ofthe circuit board (CB) 660.

In an embodiment, assuming the current source 610 is accurate, LED chaincurrent need not be measured, as it is practically identical to the setcurrent (Iset). Components 602-607 form a system measuring the LEDchain's voltage. Components 602-607 measure the “Gross Chain Voltage”620. The controller (216 in FIG. 2A) subtracts the predicted resistivelosses (estimated as the product of the wire and PCB resistance measuredin an evaluation phase with the Iset current) from the gross chainvoltage 620 to obtain the net forward voltage Vf. Once forward voltageVf and forward current If are known, it is possible to calculate thejunction temperature (Tj) based on data collected during the evaluationphase. As mentioned above, the current source 610 is not shared by theLED chains, the control component 608 is shared, and components 602through 607 may be unique or shared in various embodiments.

In an embodiment, the control component 608 is commanded by thesystem-on-module (SOM), through the Base-Board FPGA and CB FPGA, to seteach chain of LEDs to its own specific current Iset. Iset can be eithera digital parallel word or a serial bus commanding the current Source610 what current it should output. Alternately, Iset can be an analogvoltage generated from within the control component 608 with a DAC. Inan embodiment, Iset is a result of a physician choosing a specificillumination level and control component 608 must not alter it duringthe periodic temperature measurement. Hence, the temperature measurementmust be transparent to the physician. Control component 608 is linked toEEPROM 609 with an I2C bus, and serves as a mediator between a parallelbus of address and data originating from the SOM and I2C. Among theplurality of data types passing from the EEPROM 609, is the informationindicating how many LED chains exist, how many LEDs exist per eachchain, LED vendor P/N, coefficients of polynomials (i.e. data used forevaluating the temperature). SW A, B, C signals 621 are optional anddesigned to cut off current from resistor ladders when inactive. SW A,B, C 621 are normally inactive, with only one of them, if any, becomingactive during a temperature measurement. In an embodiment, during atemperature measurement, the activity of SW A, B, C is defined as: LEDchain of one LED: none; LED chain of two LEDs: SW A; LED chain of threeLEDs: SW B; and, LED chain of four LEDs: SW C. SEL 622 is a parallel businstructing which input the “Analog Mux” 606 should choose. SEL 622 isaligned with SW A, B, and C 621 when measured voltage needs to be thatof the resistive ladders 603. However, in an embodiment, SEL 622 hasextra two combinations compared with SW A, B and C 621 which are forself-calibration measurements: 10 mV and 2.5 V. Control component 608also interfaces the ADC 604 with a bus to command it to start aconversion sequence and to consequently read the conversion result. Saidresult is then passed on throughout CB's 660 FPGA fabric to SOM (via theBase-Board and its FPGA) or to a CB or BB FPGA-internal controlleroverseeing the temperature measurement.

As explained earlier, the relationship between forward voltage andjunction temperature of an LED is known only for a specific forwardcurrent (If). FIG. 7 illustrates voltage-temperature curves 701, 702 and703 for forward currents of 80 mA, 50 mA and 30 mA, respectively. One ofordinary skill in the art would appreciate that LED manufacturersnormally do not provide the voltage-temperature relationship functionover a broad range of currents, nor do they guarantee the tolerance ifand when such a relationship is provided. Therefore, in an embodiment,the method of present specification provides a prototype evaluationprocess for every model of LED installed in the distal tip. The purposeof the process is to build for various values of current in a broadrange, a function that best calculates a LED's junction temperaturebased on its voltage. This function may be computed for example, forcurrents ranging from 5 mA through 80 mA, in steps of 5 mA (i.e., 5, 10. . . 80 mA).

FIG. 8 is a flow chart showing the steps of an exemplary evaluationprocess and temperature-voltage function computation for a given LEDthat is used in the distal tip in accordance with an embodiment of thepresent specification. In an embodiment, the process is carried outmanually, by an operator. Referring to FIG. 8, in the first step 801,the LED is mounted on a PCB, wherein the PCB is the same as normallyused in the distal tip. Next, in step 802 a thermocouple is attached toa temperature measuring point defined by the LED manufacturer. Forexample, this point is defined as “Ts Point” in Nichia® LEDs, solderpoint in some Lumileds® LEDs, or thermal pad in other Lumileds® LEDs.Thereafter, in step 803, the PCB along with the LED is placed in anoven, with the thermocouple and LED current supply wires routed throughthe oven door. The following steps are then repeated for everythermocouple temperature in the range of 40 degrees C. to 135 degrees C.(or lower, in some LED models) in increments of 5 degrees C. (forexample), as indicated by steps 804, 810 and 811. The oven ambienttemperature (Ta) is adjusted such that the thermocouple (Ttc)temperature is desired and stable, as shown in step 804.

For a given Ttc, the subsequent steps are repeated for every current inthe range 5 mA to 80 mA (for example) in steps of 5 mA (for example), asindicated by steps 805, 808 and 809. After setting the LED current to adesired value, LED voltage (Vf) and current (If) values are logged, asshown in step 806. Thereafter, in step 807, junction temperature of theLED, Tj is calculated as follows:P (approximate dissipated power of LED)=Vf×If.Then, for an LED with a “Ts Point” (Nichia®), for example: Tj=Ttc+Rjs×P;Where Rjs is junction-“Ts point” thermal resistance.Again, for example, for an LED with a solder point defined as reference(Lumileds®):Tj=Ttc+Rjc×P;

Where Ttc is LED's case temperature and Rjc is junction-case thermalresistance.

After logging values of Vf, If and Tj for each LED current step and eachdesired thermocouple temperature (Ttc), all logged Vf samples areordered into bins of LED currents

(If), as shown in step 812. Then, per each If bin, operator finds thepolynomial that best fits the function Tj =Fvi(Vf) for a specific If, asshown in step 813. The values for polynomial Fvi corresponding to all Ifbins are then stored in the EEPROM.

In an embodiment, the above process is repeated for LEDs of the samemodel but of older age and/or a longer operation history to determinehow these factors affect the Voltage-Temperature curve.

In an embodiment, an evaluation process is also carried out for everymodel of endoscope using a sample of endoscopes from that model. In someembodiments, the process described below also includes measuring theresistance of the wire running between the distal tip of the endoscopeand the controller (216 in FIG. 2A) and the resistance of PCB traces, asthese may vary between endoscope types. This process, in an embodiment,is carried out manually by an operator, and is illustrated by means of aflowchart in FIG. 9. Referring to FIG. 9, for every chain of LEDs withinthe endoscope under evaluation, the total (supply and GND) resistance ofwires used to supply currents to that chain is measured, as shown instep 901. It should be noted that step 901, the measurement ofresistance, comprises a series of sub-steps, with the first sub-step 902comprising replacing the LEDs with zero Ohm resistors or wires in thesample endoscope. In the next sub-step 903, a current is driven throughthe LED chain, which is high enough to increase the accuracy ofmeasurement, yet low enough to simulate practical LED currents. In thenext sub-step 904, voltage on the current source located on the circuitboard of the endoscope is measured. This voltage is the total resistiveloss of distal tip PCB, wires, connectors, and the camera board. In thenext sub-step 905, the voltage measured in the previous step is dividedby the current, to obtain the resistance. The value of total resistancehelps in computing resistive voltage drop across the LED chain, and incalculating the net chain voltage, Vf. This is described in furtherdetail below with respect to FIG. 10. One of ordinary skill in the artwould appreciate that compensating for the total resistance (of wires,connectors, etc.) is important for accurate measurement of voltage, andhence, temperature at the LEDs.

In step 906 of the evaluation process, the mathematical connectionbetween the distal tip external temperature (Tdt) and average Tj(junction temperature of an LED) is computed. For measuring the externaltemperature, in embodiments, thermocouples are attached to key points atexternal sides of the distal tip, as shown in 907. Thereafter, a seriesof sub-steps are executed, which are repeated for every current in therange 5 mA to 80 mA (for example) in incremental steps of 10 mA (forexample), as shown by sub-steps 908, 913 and 914. After setting theLEDs' current to the desired value, Tj is logged for every LED chain,using the method described in FIG. 8, as shown in sub-step 909. Then insub-step 910, Tdt is logged for every thermocouple attached to thedistal tip. Thereafter average Tj is calculated in step 911.

In an embodiment, sub-steps 909, 910, and 911 are repeated for everycooling scheme that the endoscope system provides. For example,pressurized gas flow flowing out through the tip of an endoscope duringa procedure is used to inflate the intestine, which prevents collapse ofthe intestinal walls on the endoscope, hence assisting in prevention ofinjuries, navigation, and observation. This gas flow also contributes todistal tip cooling since it is a means of forced convection heatdissipation. Thus, in an embodiment, the aforementioned steps arerepeated for various levels of gas flow, such as 0% gas flow, 33% gasflow, 66% gas flow, and 100% gas flow. The steps are also repeated forthe situation when water jets are employed along with 100% gas flow.

Finally, in step 912, the polynomial that best fits the functionTdt=Fidt(Tj) for the given LEDs' current is determined.

In an embodiment, for every endoscope manufactured, the endoscope'sEEPROM is programmed with at least one of, and preferably a combinationof, the following parameters:

-   -   Date of manufacture;    -   For every current measured, and per every point on the distal        tip, a set of polynomial coefficients describing Tdt=Fidt(Tj)        for the specific current and point on the distal tip;    -   Number of LED chains;    -   For each LED chain, the resistance of wires, number of LEDs in        the chain, whether each LED is realized as single LED, or two        LEDs connected in parallel, model ID of LEDs; and    -   For each value of current used in the prototype evaluation        process, the value of current, set of polynomial coefficients        describing Tj=Fvi(Vf) (i.e., junction temperature vs. voltage,        per given value of current).

In an embodiment, when an endoscope is in operation, the controller ofthe endoscope system periodically programs the endoscope's EEPROM withthe elapsed operation time per each LED, categorized into illuminationintensity bins. This logging of operational profile (or working age) ofLEDs can assist in real time fitting of the Voltage-Temperature curveaccording to any given time, by knowing the operational profile up tothat specific point of time. Further, measurements done for a newlyassembled distal tip can be repeated for an aged distal tip of knownoperational profile, to investigate how aging and accumulatingoperational hours affect the Voltage-Temperature characteristics of thedistal tip.

In an embodiment, for every endoscope it is verified that measuring thedistal tip temperature at predetermined select setup conditions oftemperatures and currents using the present method approximates wellwith measuring with an external thermocouple.

In an embodiment, the system uses BIT (Built-In Test) for its ADCs(Analog-to-Digital Converters, described earlier with reference to FIG.6) by channeling the precise voltage references to inputs of ADCs andthen verifying that readouts are within permitted tolerances. In anembodiment, such Built-In Tests are performed once upon system power-up.Further, in an embodiment, if ADCs are suspected of not meeting with therated accuracy, the system periodically self-calibrates using thefollowing relationships:

For every ADC, the ideal relationship between N (digital readout) andVin (input voltage) is: Vin=A×N +B; where A and B are coefficientsrepresenting gain and offset respectively. The closer A is to the idealtheoretical gain, the more accurate the ADC. Additionally, the closer Bis to zero, the more accurate the ADC.

The ADC is calibrated with up-to-date A and B coefficients, using thefollowing equations:A=(V2−V1)/(N2−N1) andB=(V1×N2−V2×N1)/(N2−N1);

Where V1=Lower reference voltage,

-   -   V2=Higher reference voltage,    -   N1 is obtained by channeling the lower reference voltage V1 to        ADCs' inputs, and obtaining an average of a few readouts, and    -   N2 is obtained by channeling the higher reference voltage V2 to        ADCs' inputs and obtaining an average of a few readouts.

In an embodiment, the controller of the endoscopy system is configuredto automatically determine the LEDs' junction temperature (Tj) anddistal tip's temperature (Tdt) when the endoscope is in operation. Thetemperature determination is based on the measurement of LED voltages,as described above with reference to FIGS. 6, 7, 8, and 9. FIG. 10illustrates the process of temperature determination according to anembodiment, using a flowchart. Referring to FIG. 10, along with FIGS. 6,7, 8, and 9, in the first step 1001, an LED chain is selected forvoltage measurement. Next, in step 1002, the system selects anappropriate resistive ladder (shown in FIG. 6) according to the numberof LEDs in the chain being measured. This information is retrieved fromthe EEPROM. The resistive ladder normalizes the ADC's reading to bealways equivalent to a single LED and also prevents ADC input fromexceeding permitted voltage.

To obtain a good accuracy and noise level, the input of ADC is sampledand then averaged, as shown in step 1003. The average result representsthe gross chain voltage, which includes all resistive voltage drops,mainly due to endoscope wires. Next, in step 1004, the resistive voltagedrop is subtracted from the gross chain voltage to obtain the net chain(LED) voltage Vf. It may be noted that the resistive voltage drop is theproduct of three factors:

-   -   1. Electric current being supplied to the LED chain, which is        known to the system since the system itself regulates that        current;    -   2. Resistance of the LED chain (mainly due to wires), which is        stored in the EEPROM; and    -   3. 1/[number of LEDs per chain]. The number of LEDs per chain is        specified in the EEPROM.

After determining net chain voltage Vf, LED's junction temperature (Tj)is calculated for all currents used in the prototype evaluation process(detailed in FIG. 8), using the newly calculated Vf. This Vf can beconsidered the average Vf over all LEDs in a chain. This is shown instep 1005. Calculation of Tj is based on the set of polynomialscoefficients stored in EEPROM, describing Tj=Fvi(Vf), for every current.

With all the junction temperatures obtained from calculating thepolynomials at all defined currents, per measured Vf, in the next step1006 the polynomial that best fits the Tj vs. If curve (per the givenmeasured Vf) is computed. Thereafter, the real Tj is calculated in step1007 by assigning the actual If value to the polynomial computed above.The actual If implies the value of current being supplied at that time,instead of any of fixed If as used in the prototype evaluation process.It may be noted that in case of two LEDs operating in parallel, actualcurrent value assigned to polynomial is If/2. Referring again to FIG. 7,the LEDs of an exemplary system are evaluated at 30 mA 703, 50 mA 702,and 80 mA 701. In an embodiment, assuming the system detects a measuredVf of 2.970 V, Tj equals 40° C. 713 at I=30 mA, Tj equals 76° C. 712 atI=50 mA, and Tj equals 120° C. 711 at I=80 mA. Using these three datapoints, a Tj vs. If trendline can be extracted. Further assuming actualIf is 45 mA, the actual (real) Tj can be determined by interpolating thethree data points. Although three data points are described in thecurrent example, the process will use a much greater number of datapoints to determine Tj.

The above steps (1001 through 1007) are repeated as previously for allthe LED chains in the distal tip, as illustrated by step 1008.

After the Tj (junction temperature) for all the LED chains is measured,the system estimates external temperature (Tdt) at all the key points onthe distal tip, which were earlier measured during the prototypeevaluation process, described with reference to FIG. 9. For thispurpose, in step 1009, Tdt is calculated for all currents used in theprototype estimation process, while assigning the newly estimated Tj toeach polynomial. Coefficients of these polynomials are stored in theEEPROM. Next, in step 1010, the polynomial that best fits the Tdt—Ifcurve for the given Tj is computed. In one embodiment, the relationshipbetween Tdt and Tj is defined as Tdt=If×K+Tj+Offset. In someembodiments, this relationship is further affected by the number of LEDchains and by the dissipation of the constant heat of the imagers.

In the next step 1011, the actual If is assigned to the polynomialcomputed above to obtain the best estimate for distal tip temperature atthat key point. The actual If implies the value of current beingsupplied at that time, instead of any of fixed If as used in theprototype evaluation process.

In an embodiment, the system displays the measured temperature on theendoscope display. In various embodiments, the temperature displayed isthe Tj, Tdt, or both.

In an embodiment, the system automatically takes one or more correctiveactions to resolve overheating in LEDs or in the distal tip exterior.Overheating conditions are reflected by the average Tj (for LEDs) oraverage Tdt (distal tip) being too high. For Tj, overheating includestemperatures too close to the maximum Tj permitted by the LEDmanufacturer (absolute maximum rating) and, in some embodiments, isequal to 120° C. For Tdt, overheating includes temperatures consideredunsafe or uncomfortable for the patient. Corrective actions may include,but are not limited to:

-   -   Reducing dissipated heat by reducing LED currents in chains        where overheating occurred, or by switching off currents in the        chains being overheated (excluding chains related to front        viewing element);    -   Intensifying cooling by autonomously increasing endoscope gas        flow and/or by activating water jets.

In an embodiment, an icon is displayed on the endoscope system screenrecommending the physician to activate the water jets. In oneembodiment, an icon or notification indicating that temperature is beingoptimized is displayed on the screen in case any of the above correctiveactions are taken, including current being reduced or switched off andincreasing cooling.

In one embodiment, an overheating event is logged in system log file.

In an embodiment, after Tj/Tdt return to nominal levels after takingcorrective measures for overheating, the system applies a hysteresismechanism when restoring intended system settings, such as LED currents.This mechanism prevents oscillation and annoying image artifacts. Thehysteresis mechanism defines different thresholds for differentscenarios. For example, in an embodiment, the threshold for setting alow value If to avoid overheating is 120° C. and a threshold forreturning If to the normal setting is 110° C.

FIG. 11 details the controller hardware that is used for computation oftemperature according to the methods detailed above, and also for takingcorrective action in case of overheating in accordance with anembodiment of the present specification. Referring to FIG. 11, thecontroller circuit board 1120 of the Main Control Unit operativelyconnects with the endoscope 1110 and the display units 1150. In anembodiment, the controller circuit board 1120 further comprises a cameraboard 1121 that transmits appropriate commands to control the powersupply to the LEDs 1111 and to control the operation of image sensor1112 (comprising one or more viewing elements), such as but not limitedto a Charge Coupled Device (CCD) or a Complementary Metal OxideSemiconductor (CMOS) imager, in the endoscope. The camera board in turnreceives video signal 1113 generated by the CCD imager and also otherremote commands 1114 from the endoscope. The circuit for measuringvoltage across the LEDs, shown and detailed with reference to FIG. 6, isalso located on the camera board 1121.

In embodiment, the controller circuit board 1120 further compriseselements for processing the video obtained from the imager 1112,including MPEG Digital Signal Processor 1122, field-programmable gatearray (FPGA), local processor 1123 that performs video interpolation andon-screen display overlay. The video signal is sent for display throughVideo output interface 1124. A video input interface 1125 is alsoprovided for receiving video input from an external analog or digitalvideo source.

FPGA 1123 is a logic device programmed specifically for systemrequirements and is associated with memory, such as DDR 1155. In anembodiment, the pre-programmed instructions from the FPGA 1123 areexecuted by Video output interface 1124 to generate appropriate videosignals for display. FPGA 1123 performs tasks that may be categorized intwo types: logic tasks which must be implemented by hardware (as opposedto software), and logic tasks related to video image processing. In anembodiment, FPGA is programmed to compute LED junction temperature anddistal tip temperature, in accordance with the method detailed in FIG.10. In some embodiments, these calculations are performed in the SOM1126, but can also be assigned to an FPGA on the camera board 1121 orthe FPGA 1123 on the base-board. FPGA 1123 is further programmed to takecorrective actions in case of overheating, such as reducing LED currentsand increasing cooling by using water jets or gas.

System on Module (SOM) 1126 provides an interface to input devices suchas keyboard and mouse, while Touch I/F 1127 provides touch screeninterface. In an embodiment, the controller 1120 further controls one ormore fluid, liquid and/or suction pump(s) which supply correspondingfunctionalities to the endoscope through pneumatic I/F 1128, pump 1129and check valve 1130. In embodiments, the controller further comprises apower supply on board 1145 and a front panel 1135 which providesoperational buttons 1140, 1141 for the user.

The camera board 1121 receives video signal 1113 which, in anembodiment, comprises three video feeds, corresponding to video pickupsby three endoscopic tip viewing elements (one front and two side-lookingviewing elements), as generated by the CCD imager 1112.

In an embodiment, the system adaptively configures image processingparameters according to measured temperatures at the distal tip, toachieve optimal image quality, regardless of whether overheating occursor not. FIG. 12A shows a graph illustrating the effect of ambienttemperature on LED chromaticity coordinate, which can affect imagerchromaticity. Referring to FIG. 12A, it can be seen from the curve 1201that for a given forward current (which is 80 mA in the presentexample), as the ambient temperature increases, chromaticity shifts moretoward blue. Another graph in FIG. 12B shows the relationship betweenLED ambient temperature T_(A) 1205 and LED relative luminous flux 1210,which is an indicator of brightness. Variations in LED luminosity canaffect image luminosity. As seen in the figure, as the ambienttemperature approaches 30° C. and then increases further, for a givenforward current (which is 80 mA in the present example), the luminousflux starts decreasing. Therefore, in an embodiment, image parametersare altered to compensate for possible changes in brightness,chromaticity and noise, which may occur due to change in temperature ofthe LED illuminators. This tuning of parameters is effectuated by thehardware components detailed above with reference to FIG. 11.

In accordance with another embodiment, the present specificationdiscloses a method to automatically regulate, control or manage theillumination, luminance or luminous intensity of the one or moreilluminators associated with each of the plurality of viewing elementsof the endoscope tip section. The terms illumination intensity,luminance intensity or luminous intensity are hereinafter usedinterchangeably as an expression of the amount of light power emanatingfrom an LED and in various embodiments is a function of electric currentflow through the LED.

In an embodiment, the luminance intensity of one or more illuminators isautomatically regulated depending upon whether the endoscope tip sectionis detected to be in an active or passive state. In various embodiments,the active state corresponds to at least one of the following scenarios:a) a movement of the endoscope tip section relative to its surroundings,environment or background, indicative of, for example, a use of theendoscope tip section in a typical endoscopic procedure, and/or b) anobject approaching or being brought at a distance of less than apredefined threshold value of distance from the endoscope tip section.In an embodiment, an active state for the tip section is defined ashaving an object approach or brought toward the tip section of theendoscope at a distance of less than or equal to 5 centimeters (d≤5 cm)from the endoscope tip section. In various embodiments, a passive statecorresponds to a scenario where the endoscope tip section is stationaryor static relative to its surroundings, environment or background. Thatis, the endoscope tip section is static or not moving or one or moreobjects in the surroundings relative to the tip section may move so longas they remain beyond a predefined distance from the endoscope tipsection.

In an embodiment, the method of the present specification automaticallymonitors and detects the active or passive state of the endoscope tipsection and, in response, automatically regulates the luminanceintensity of the one or more illuminators. In various embodiments, whenthe endoscope tip section is in the active state, the luminanceintensity of the one or more illuminators is automatically set to afirst intensity level. In some embodiments, the first intensity levelcorresponds to a default operating intensity level or to an intensitylevel manually set by a physician as per his preference. In variousembodiments, the first intensity level corresponds to electric currentflow, through one or more illuminators, ranging from about 20 mA to 100mA, and more preferably 40 mA to 50 mA.

In various embodiments, when the endoscope tip section is in a passivestate, the luminance intensity of the one or more illuminators isautomatically set to a second intensity level. The second intensitylevel is either default intensity or manually set by the physician asper his preference. In various embodiments, the second intensity levelis lower than the first intensity level. In some embodiments, the secondintensity level is such that at this second intensity the one or moreilluminators generate substantially lower heat in the endoscope tipsection while still enabling the one or more illuminators to beilluminated and identifiable to indicate to the physician that the oneor more illuminators are functioning. In some embodiments, the secondintensity level corresponds to zero intensity which means that the oneor more illuminators are switched off at the second intensity level. Invarious embodiments, the second intensity level corresponds to electricflow, through one or more illuminators, ranging from about 0 mA to 19mA, and more preferably, 0 mA to 2 mA.

In an embodiment, the first and second intensity levels are differentfor each of the illuminators present in the system.

In accordance with various embodiments, the method of the presentspecification enables proximity detection by sensing the endoscope tipsection to be in the active state when at least one object from thesurroundings, environment or background approaches or is brought nearthe endoscope tip section at a distance of less than a predefinedthreshold value of distance ‘d’. This proximity detection feature isadvantageous since the physician can activate or set the one or moreilluminators to the first intensity level by simply bringing their handwithin the distance ‘d’ of the one or more illuminators withoutphysically contacting the illuminators. In some embodiments, theproximity detection feature is enabled by default and can be disabled ifneeded. In some embodiments, the proximity detection feature can beenabled or disabled manually.

Reference is now made to FIG. 13A which is a flow chart illustrating aplurality of exemplary steps of a method 1300 of automatically detectingthe active or passive state of the endoscope tip section (such as thetip section 230 of FIG. 2C) and accordingly regulating the luminanceintensity of one or more illuminators, associated with a plurality ofviewing elements of the endoscope tip section, to the first or thesecond intensity level. Persons of ordinary skill in the art shouldappreciate that the sequence of steps of the method 1300 are onlyexemplary and the sequence may change in alternate embodiments. Invarious embodiments, the method 1300 is implemented as software or aplurality of programmatic codes executed by a processor of a MainControl Unit, such as the MCU 216 of FIG. 2A, associated with theendoscope tip section.

In an embodiment, the method 1300 assumes an initialization stage 1305where the one or more illuminators are switched on and a programmatictimer or counter is also initialized. At step 1310 a, when the timer orcounter is at a first time instance value such as t₀, a first sample isacquired of at least one image generated by the plurality of viewingelements of the endoscope. In one embodiment, the endoscope tip sectionincludes three viewing elements—a front pointing viewing element, afirst side pointing viewing element and a second side pointing viewingelement (as shown in the tip section 230 of FIG. 2C). Thus, in thisembodiment, at least one and up to three corresponding images aregenerated or captured by the three viewing elements. It should beappreciated that in various alternate embodiments with the endoscope tipsection comprising one or two viewing elements the number ofcorresponding images generated are at least one and up to two. In apreferred embodiment, the first sample includes three image framescorresponding to three viewing elements of the endoscope tip section.

At step 1315 a, luminance (Y) component is extracted for the pixels ofeach of the images (such as three images corresponding to three viewingelements in one embodiment) of the first sample captured at time t₀. Atstep 1320 a each of the images, of the first sample, is divided orsegmented into a plurality of blocks of n x m pixels. In an embodiment,each block is of size 20×20 pixels, yet block size may be smaller orlarger than 20×20 pixels. Thereafter, at step 1325 a, an averageluminance for each block is calculated for each image of the firstsample.

At step 1310 b, when the timer or counter is at a second time instancevalue such as t₁, a second sample is acquired of at least one imagegenerated by the plurality of viewing elements of the endoscope. In anembodiment, the second sample includes three image frames correspondingto three viewing elements of the endoscope tip section. In anembodiment, the time difference between t₀ and t₁ is about 0.5 seconds,yet the time difference between t₀ and t₁ may be smaller or larger than0.5 seconds. In the embodiment wherein the time difference between t₀and t₁ is about 0.5 seconds, every 15th image frames are sampled(assuming 30 frames per second as the frequency of frames). Next, atstep 1315 b, luminance (Y) component is extracted for the pixels of eachof the images (such as three images corresponding to three viewingelements in one embodiment) of the second sample captured at time t₁. Atstep 1320 b each of the images, of the second sample, is divided orsegmented into a plurality of blocks of n×m pixels. In an embodiment,each block is of size 20×20 pixels, yet block size may be smaller orlarger than 20×20 pixels. Thereafter, at step 1325 b, an averageluminance for each block is calculated for each image of the secondsample.

Now, at step 1330 for each block an average luminance absolutedifference or change is calculated between the corresponding images ofthe first and second samples (obtained at t₀ and t₁). In accordance withan embodiment, the average luminance absolute difference or change iscalculated for each block of all three images obtained from the threeviewing elements in the first and second samples. At step 1335, for eachblock, the maximum of the average luminance absolute difference orchange is chosen from among the three sets of images obtained from thethree viewing elements. At step 1336, a luminance histogram is computedas a count of the number of pixels for each luminance value in arepresented range, such as 0 to 255 in case of 8 bits pixelrepresentation.

Next at step 1340, for each block, the value of maximum averageluminance absolute difference or change is compared against a firstthreshold luminance value, also referred to as a local threshold todetermine or identify those blocks whose maximum average luminancechange exceeds the first threshold luminance value. At step 1345, acount of the blocks is computed for which the maximum average luminanceabsolute difference value is found to exceed the first or localthreshold or, alternately, a fraction is computed of such blocks withreference to the total number of blocks of step 1340. It should beappreciated that the first threshold luminance value or the localthreshold is determined based on calibration and is dependent upon aplurality of factors such as, but not limited to, the type of imagesensor (CCD or CMOS), number of pixels in the image sensor, size ofpixels in the image sensor, type of illuminators (white light LED, aninfrared light LED, a near infrared light LED, an ultraviolet light LEDor any other LED), type of endoscope (colonoscope, gastroscope orbronchoscope).

Finally, at step 1350, the count or fraction of the blocks (for whichthe maximum average luminance absolute difference value is found toexceed the first or local threshold) is compared against a secondthreshold count, amount or fraction of blocks, also referred to as aglobal threshold. Depending upon whether the count or fraction of blocksdoes or does not exceed the second or global threshold, a decision(described further with reference to FIG. 3B) is made at step 1355 of atleast whether the luminance intensity of the one or more illuminatorsshould or should not be automatically changed from the first intensitylevel to the second intensity level or vice versa. It should beappreciated that the second threshold count or the global threshold isdetermined based on calibration and is dependent upon a plurality offactors such as, but not limited to, the type of image sensor (CCD,CMOS, number of pixels, size of pixels, etc.), type of illuminators(white light LED, an infrared light LED, a near infrared light LED, anultraviolet light LED or any other LED), type of endoscope (colonoscope,gastroscope or bronchoscope),In various embodiments, the first andsecond threshold values are computed respectively, for example, at steps1338 and 1346 based on the luminance histogram computed at step 1336 andby also taking into account the on/off state (referenced as 1339) of theone or more illuminators. It should be appreciated that the first orlocal threshold is computed for each block while the second or globalthreshold is computed for an entire image frame. In various embodiments,the first or local threshold is the number of pixels that have highluminance value as reflected in the luminance histogram. If the one ormore illuminators is/are switched off then the first threshold is asubstantially small value while the first threshold is a substantiallylarge value if relatively higher number of illuminators are switched on.Similarly, the second or global threshold is the number, count orfraction of blocks that have high luminance value based on the luminancehistogram. If the one or more illuminators is/are switched off then thesecond threshold is a substantially small value while the secondthreshold is a substantially large value if relatively higher number ofilluminators are switched on.

It should be appreciated that in an embodiment, if the amount orfraction of blocks with luminance change (above the first or localthreshold) is below the second or global threshold it is indicative thatonly a small portion of the images may have changed between the firstand second samples. This indicates that the endoscope tip section is inpassive state or is stationary relative to its surroundings, environmentor background. That is, the endoscope tip section is static or notmoving although one or more objects in its surroundings, environment orbackground may move—but remain beyond a predefined distance ‘d’ from theendoscope tip section. However, if the amount or fraction of blocks withluminance change (above the first or local threshold) is above thesecond or global threshold it is indicative that a sufficiently largepart of the images have changed between the first and second samples.Thus, this indicates that the endoscope tip section is in active stateas a result of at least one of the following scenarios: a) a movement ofthe endoscope tip section relative to its surroundings, environment orbackground, indicative of, for example, a use of the endoscope tipsection in a typical endoscopic procedure b) an object approaches or isbeing brought at the predefined distance ‘d’ or less than that from theendoscope tip section. In one embodiment, the predefined distance ‘d’ is5 centimeters.

Reference is now made to FIG. 13B which is a flow chart illustrating aplurality of additional steps and outcomes with reference to thedecision step 1355 of FIG. 13A. Referring now to FIG. 13B, at step 1355if the count or fraction of blocks, with high luminance difference orchange, exceeds the second or global threshold then at step 1360 it isdetermined if the one or more illuminators is/are at the first intensitylevel which, in an embodiment, corresponds to a switched on state. Ifthe one or more illuminators is/are at the first intensity level (i.e.in a switched on state), then at step 1365 a a programmatic timer orcounter is reset to a predefined positive integer value to allow the oneor more illuminators to continue to be at the first intensity level orin the switched on state. That is, resetting the timer or counter to thepositive integer value prevents the one or more illuminators fromtransitioning to the second intensity level, which in an embodimentcorresponds to a switched off state, while the endoscope tip section isin the active state. In various embodiments, the programmatic timer orcounter is a count-down timer that runs from a positive integer value toa zero value. If the one or more illuminators is/are at the secondintensity level or in a switched off state, then at step 1365 b the oneor more illuminators is/are automatically changed, regulated ortransitioned to be at the first intensity level or switched on state.

However, at step 1355, if the count or fraction of blocks with highluminance change do not exceed the second or global threshold then atstep 1370 it is determined if the one or more illuminators is/are at thefirst intensity level or in switched on state. If the one or moreilluminators is/are at the first intensity level or in switched onstate, then at step 1375 it is determined if the programmatic timer orcounter has reached the value zero. If yes, then at step 1380 a, the oneor more illuminators is/are automatically transitioned to be at thesecond intensity level or in switched off state. If no, then at step1380 b the programmatic timer or counter is advanced—that is, its valueis decreased by one. In some embodiments, the positive integer valueassigned to the timer or counter represents the maximum amount ofpredetermined time for which the one or more illuminators are allowed tostay at the first intensity level or switched on while the endoscope tipsection is in the passive state. In other words, the one or moreilluminators are set to be at the second intensity level or in switchedoff mode automatically after elapse of the predetermined time if the tipsection in the passive state (that is, the count or fraction of blocks,with high luminance change, does not exceed the second or globalthreshold).

If, at step 1370, it is determined that the one or more illuminatorsis/are at the second intensity level or in a switched off state then atstep 1385 the one or more illuminators are allowed to remain at suchsecond intensity level or in a switched off state.

Referring back to FIGS. 2C and 2A, in various embodiments, the pluralityof illuminators, such as the illuminators 242 a, 242 b, 242 c, 252 a,252 b, 272 a and 272 b, are connected in parallel to a power supplyline. Each of the plurality of illuminators further comprises anilluminator circuit (an embodiment of which is described with referenceto FIG. 14) configured to control the illuminator's illumination orluminance intensity level according to control signals, generated by theprocessor of the MCU 216 of FIG. 2A, using the method of FIGS. 13A, 13B.The control signals comprise instructions for switching on and off eachilluminator independent from other illuminators under a specificparallel connection and for varying the intensities of each illuminatorindependently. In an embodiment, a maximal upper bound allowed currentthrough each one of the plurality of illuminators is used to manage heatproduction in an illuminator or the endoscope's tip section, where theprocessor of the MCU 216 reduces currents in one or more illuminatorsaccordingly, as a result of the implementation of the method of FIGS.13A, 13B.

Reference is now made to FIG. 14, which illustrates an illuminatorcircuit in a block diagram, according to certain embodiments.Illuminator circuit 1400 includes a power supply input pin ANODE 1401 onwhich a control signal is superimposed and a ground input pin GND 1402.ANODE pin 1401 is in electrical communication with or connected to avoltage regulator 1403, a capacitor 1405, a Zener diode 1413 and acurrent source 1407 which is connected further to a n-channel transistor1409. Zener diode 1413 is in electrical communication with or connectedto resistor 1415 and to analog-to-digital (A/D) converter 1417. Logiccircuit 1420 receives A/D′s 1417 digitized output signal, and comprisesa DC extraction module 1422, a data extraction module 1424 and aregisters and control module 1426. Logic circuit 1420 is configured toextract the inputted power supply DC level with the assistance of DCextraction module 1422 and to decode control signal instructions withthe assistance of data extraction module 1424.

In various embodiments, data extraction module or circuit 1424 includesa UART (universal-asynchronous-receiver-transmitter) decoder that isused to decode communicated UART instructions transmitted over the powerline (FIG. 15A 1550) which is connected to input pin ANODE 1401. In anembodiment, the UART protocol is a UART 9,600 bits per second protocol,includes a start bit, 1 even parity bit and 1 stop bit added to eachtransmitted byte.

According to various embodiments, the first UART communicated byte is anilluminator device ID, where LSB (least significant byte)=1 encodes aUART read instruction and LSB=0 encodes a UART write instruction. Thesecond communicated byte is a 4 bit LED-enable bits and the remaining 4bits is an accessed register address. The third communicated byte is adata byte and the fourth communicated byte is a checksum byte.Accordingly, total number of bits transmitted per one UART instructionis 44 bits. Transmitting a 44 bits UART instruction lasts 4.5milliseconds, where 104 micro seconds is a 1 bit transmission timeduration of a UART 9,600 protocol.

In an embodiment, logic circuit 1420 is implemented as an ASICprocessor. However, other processor types, such as field programmablegate arrays (FPGAs), and the like, are used in certain embodiments.According to certain embodiments, logic circuit 1420 is implemented by aminiature FPGA (for example, 1.5 mm×1.5 mm FPGAs, or less, including thepackage are already available).

Logic circuit 1420 is configured to generate a digitized control valuedecoded by the UART decoder and used to determine the desired currentflow through LED 411. In this example, the illuminator circuit containsjust a single LED. However, in other embodiments, illuminator circuitmay contain more than one LED. The digitized control value is filteredusing a low pass filter logic module 1428 before it is converted to ananalog signal by digital-to-analog (D/A) converter 1431 and is inputtedto operational-amplifier (Op-Amp) 1433 non-inverting input. Low-passfilter 1428 is used for soft-start switching on and off LED's (1411)current gradually, minimize voltage under/over-shoot on power supply pin1401 while LED's 1411 current is changing.

Op-Amp 1433 output is connected to the gate of an n-channel field-effecttransistor (FET) 1435, whose source is connected to the inverting(feedback) input of Op-Amp 1433. A drain for FET 1435 is connected to acathode of LED 1411 and its source to resistor (Rs) 1437. Theillumination or luminance intensity, i.e. electric current flow, of LED1411 is practically identical to that of Rs 1437. This electric currentflow is controlled by Op-Amp 1433 by means of feedback: Op-Amp 1433 setsits output (hence, FET 1435 gate node) to such a voltage, that theresulting voltage at its inverting (feedback) input is identical to thatof its non-inverting input which is the extracted control signal UARTinstruction. Hence, the resulting electric current that flows throughFET 1435 and LED 1411 is configured to be the desired UART instruction'svoltage divided by the resistance of Rs 1437.

According to certain embodiments, UART protocol is used to communicatecontrol signal instructions over power line 1550 (see FIG. 15A).However, other standard or non-standard communication protocols, such asthe serial peripheral interface (SPI) protocol, are used to communicatecontrol signals over power line 1550 (FIG. 15A) in other embodiments.

According to certain embodiments, UART write instructions aretransmitted in broadcast mode, i.e. addressing a plurality ofilluminators simultaneously, and/or allowing a multiple number of LEDsto be turned on or off simultaneously.

According to certain embodiments, power line communication (PLC) knowntechniques, adapted to DC power, are used to modulate UART, or othercommunication protocol that may be used.

In an embodiment, the illuminator circuit 1400 includes power-on-resetmodule 1440 configured to reset logic 1420 to a known state upon powerup.

In an embodiment, the illuminator circuit 1400 includes motion sensor1450 that may be a gyro and/or an accelerometer configured to measure ormaintain orientation of endoscope tip section 230 of FIG. 2C.

In an embodiment, the illuminator circuit 1400 includes oscillator 1460configured to generate internal clock signal for illuminator circuit1400. Frequency of oscillator 1460 may be, for example, in the range of500 KHz to 1MHz.

In an embodiment, the illuminator circuit 1400 includes non-volatilememory cells (NVRAM) 1470 configured to store digital data such as:device parameters; illuminator part number; illuminator vendor ID;illuminator ID; records of operational hours per current range.

In an embodiment, temperature sensor 1480 is configured to measure theilluminator junction temperature at a plurality of junctions inilluminator circuit 1400, from which the endoscope tip section'sequivalent temperature may be calculated.

In an embodiment, FET 1409 switches current source 1407 (with optionalsoft-start), to transmit telemetry data back to processor 1510 (FIGS.15A, 15B), in response to the instructions of processors 1510 (FIGS.15A, 15B).

In an embodiment, A/D 1439 is configured to tap FET's 1435 drain, suchthat processor 1510 (FIGS. 15A, 15B), in response to a read requestinstruction, may be configured to determine if ANODE 1401 voltage iswithin a desired range (i.e. FET 1435 drain voltage is high enough suchthat FET 1435 functions as a current regulator, and not too high, suchthat FET 1435 overheats illuminator circuit 1400).

In an embodiment, illuminator circuit 1400 includes a third input pinused to communicate instructions not superimposed on power line 1550(FIG. 15A).

Reference is now made to FIG. 15A, which illustrates a parallelilluminating system circuit, according to certain embodiments. Parallelilluminating system circuit 1500 includes switched voltage regulator1502 current sense resistor 1503, linear voltage regulator 1504,differential amplifier 1506, A/D converter 1508, D/A converter 1512 andprocessor 1510. FIG. 15A is an example, in which the parallelilluminating system circuit 1500 includes three illuminator circuits1520, 1530 and 1540 connected to single power supply line 1550. However,in actual systems the number of illuminator circuits connected to asingle line may be substantially higher.

In an embodiment, the single power supply line 1550 is the camera board(CB) power supply line of an endoscope. Typically, endoscope's CB powersupply line may be 3 to 4 meters long, and may carry typically 40 mAcurrent flow per illuminator in regular (yet maximal) illuminationconditions, and 150 mA current flow per illuminator in flashillumination mode. U.S. patent application Ser. No. 14/274,323 entitled“An Endoscope Tip Position Visual Indicator and Heat Management System”,and filed on May 9, 2014 by the Applicant of the present specification,discloses an endoscope having a tip section equipped with multipleviewing elements, wherein each of the viewing elements' field of view isilluminated by a discrete illuminator, such as a LED, being operated ina flash mode, and is herein incorporated by reference in its entirety.

In an embodiment, the processor 1510 is a camera board (CB) circuitprocessor located in an external control unit (such as the MCU 216 ofFIG. 2A) connected to the endoscope and to a display or in the endoscopehandle.

Illuminator circuits 1520, 1530 and 1540 comprise the illuminatorcircuit illustrated and described with respect to FIG. 14 above whereinthe power line 1550 is connected to FIG. 14 input pin ANODE 1401 and GND1560 is connected to FIG. 14 input pin GND 1402 for each illuminatorcircuit 1520, 1530 and 1540. In embodiments, the processor 1510 may bean FPGA, an ASIC, a software-controlled processor and the like. Inaccordance with an aspect of the present specification, the processor1510 implements the method of FIGS. 13A, 13B and is therefore asoftware-controlled processor. Processor 1510 is configured to generatecontrol signal instructions (using the method of FIGS. 13A, 13B) inorder to vary the illumination intensity of each illuminator 1520, 1530and 1540 connected in parallel to power line 1550. Processor 1510switches on or off each illuminator and regulates the illumination orluminance intensity of each illuminator independent from the operatingcondition of other illuminators. In an embodiment, the processor 1510 isconfigured to generate control signal instructions to illuminators 1520,1530 and 1540 automatically after processing of the images capturedusing a plurality of viewing elements. Processor 1510 is configured toperform image processing by executing an image processing softwareprogram code (method of FIGS. 13A, 13B) stored in the processor memory.In an alternate embodiment, the processor 1510 includes an imageprocessing hardware circuit.

In some embodiments, the processor 1510 is configured to vary theillumination intensity of illuminators 1520, 1530 and 1540 according tomanual instructions of a surgeon via a user interface.

In an embodiment, processor 1510 is configured to regulate theillumination intensity of illuminators 1520, 1530 and 1540 according tothe endoscope tip section's temperature calculated by measuring thetemperature at the illuminator junction (using temperature sensor 1480as shown in FIG. 14).

In an embodiment, the processor 1510 is configured to regulate theillumination intensity of illuminators 1520, 1530 and 1540 based on thefeedback received from a motion sensor 1450 (FIG. 14) indications. Inembodiments, motion sensor 1450 is a Micro Electro-Mechanical System(MEMS) accelerometer or gyro.

In an embodiment, processor 1510 is configured to switch on and offilluminators allocated to special operational modes, for example NBI.

In an embodiment, the processor 1510 uses the output of A/D 1508 tocalculate the current flowing through power line 1550 (i.e. loadcurrent), as part of built-in test (BIT) module whose purpose is toverify that each illuminator draws the current that it is configured todraw.

In an embodiment, the processor 1510 uses the output of A/D 1508 tocalculate the current flowing through power line 1550 (i.e. loadcurrent), and then increase the output VCB of the Line Voltage Regulator1504 to compensate for the voltage drops caused by the resistance inpower line 1550 and the load current. This method of compensation isonly effective if the processor 1510 is provided in advance with thevalue of electrical resistance of power line 1550.

In an embodiment, the processor 1510 is informed by the MCU 216 (FIG.2A) about the resistance of power line 1550, after the MCU 216 queriesthe newly inserted endoscope about its type.

In an embodiment, the processor 1510 is configured to calculate theactual resistance of power line 1550, by reading from the illuminatorstheir power supply (ANODE 1401 of FIG. 14) voltage. Accordingly, thedifference between the desired VCB and the illuminators' supply voltage,divided by the current measured by the Sense Resistor (1503) andconverted by A/D (1508) is the actual resistance.

According to embodiments of the present specification, more than oneparallel illuminating system circuit, described in FIG. 15A hereinabove,may be implemented, thereby reducing the current load from the powerline and increasing the communication throughput.

Reference is now made to FIG. 15B, which illustrates the parallelilluminating system of FIG. 15A further incorporating a remote sense,according to certain embodiments. In an embodiment, the parallelilluminating system circuit 1500 includes remote sense line 1570. In anembodiment, the remote sense line 1570 is configured to provide ameasure of the actual voltage applied on the illuminators circuit inputsin order to provide the desired operational condition. In an embodiment,the remote sense line 1570 is configured to detect a voltage fall, dueto supply line's 1550 load, and the processor 1510 is configured tocompensate the voltage fall by increasing the applied voltage VCB 1580.

FIG. 16 is a block diagram illustration of another embodiment of anilluminator circuit 1600. The circuit 1600 includes non-volatile memorycells (NVRAM) 1605 configured to store digital data such as, but notlimited to, voltage data. The stored digital voltage value 1606 isapplied to a digital to analog convertor 1610 that outputs acorresponding analog voltage 1612. The analog voltage 1612 is input to avoltage regulator 1615 that converts the input analog voltage 1612 tocorresponding current for supplying to one or more LEDs 1620, which maybe connected in series in accordance to some embodiments.

FIG. 17 is a block diagram illustration of yet another embodiment of anilluminator circuit 1700. The circuit 1700 includes a processor 1705which in various embodiments may be an FPGA, an ASIC, asoftware-controlled processor and the like. In accordance with an aspectof the present specification, the processor 1705 implements the methodof FIGS. 13A, 13B and is therefore a software-controlled processor.Processor 1705 is configured to generate control signal instructions(using the method of FIGS. 13A, 13B) in order to vary the illuminationintensity of one or more LEDs 1730 that may be connected in series insome embodiments. Control digital signals from the processor 1705 arereceived by the digital to analog converter (DAC) 1710 that converts thedigital signals, such as digital voltage, into analog signals (analogvoltage). The analog signals, output from the DAC 1710 are input to avoltage regulator 1715 that in turn applies an analog current to the oneor more LEDs 1730. A first feedback line 1716 from the voltage regulator1715 conveys the analog current level generated at the voltage regulator1715 back to the processor 1705 via a current measurement amplifier 1717and an analog to digital converter (ADC) 1718. Also, a second feedbackline 1720 from the voltage regulator 1715 conveys the analog voltagelevel at the voltage regulator 1715 back to the processor 1705 via avoltage measurement element 1721 and an analog to digital converter(ADC) 1722.

The above examples are merely illustrative of the many applications ofthe system of present invention. Although only a few embodiments of thepresent invention have been described herein, it should be understoodthat the present invention might be embodied in many other specificforms without departing from the spirit or scope of the invention.Therefore, the present examples and embodiments are to be considered asillustrative and not restrictive, and the invention may be modifiedwithin the scope of the appended claims.

We claim:
 1. An endoscopy system comprising: an endoscope having a tip;a plurality of viewing elements located at the endoscope tip, whereineach of said viewing elements comprises an image sensor having a fieldof view illuminated by one or more light emitting diode (LED)illuminators; a circuit board comprising a circuit for measuring avoltage across each of said LED illuminators; and a controllerprogrammed to compute a temperature of each of said LED illuminators byusing said measured voltage and a function representing a relationshipbetween LED voltage and LED junction temperature for a given current,wherein the controller is further programmed to compute an average ofLED junction temperatures and use that average to compute thetemperature at a given point on the endoscope tip, and wherein arelationship between the average of LED junction temperatures and thetemperature at the given point on the endoscope tip is pre-determined bymeasuring an average LED junction temperature and a correspondingtemperature at the given point on the endoscope tip for a range of LEDcurrents and identifying a relationship between average LED junctiontemperatures and temperatures for the given point on the endoscope tip.2. The system of claim 1, wherein the controller is further programmedto reduce a power of the LED illuminators if the average LED junctiontemperature exceeds a pre-determined limit.
 3. The system of claim 1,wherein the function representing the relationship between LED voltageand LED junction temperature is pre-determined by measuring LED voltageand LED junction temperature for a range of LED currents and identifyinga relationship between LED voltage and junction temperature.
 4. Thesystem of claim 1, wherein said relationship is estimated usingregression analysis.
 5. A method for determining a temperature in anendoscope, without using a separate, dedicated temperature sensor,wherein said endoscope comprises a plurality of viewing elements locatedat a distal tip of the endoscope and wherein each of said viewingelements comprises an image sensor having a field of view illuminated byone or more LED illuminators, said method comprising: measuring avoltage across at least one of said LED illuminators; computing ajunction temperature for the at least one of said LED illuminators byusing a value of the measured voltage and a function representing arelationship between LED voltage and LED junction temperature for agiven current and for the at least one of said LED illuminators; andcomputing an average of junction temperatures of at least two LEDilluminators present in the endoscope and using that average to computethe temperature at a given point on the distal tip; wherein an averageof junction temperature of only the LED illuminators, which are directlyadjacent the given point on the distal tip, are used to estimate thetemperature at said given point.
 6. The method of claim 5, wherein anaverage of junction temperatures of all the LED illuminators is used toestimate the temperature at the given point on the distal tip.
 7. Themethod of claim 5, wherein a power of the at least one of said LEDilluminator is reduced if a junction temperature of said LED illuminatorexceeds a pre-determined limit.
 8. The method of claim 5, wherein thefunction representing the relationship between LED voltage and LEDjunction temperature is pre-determined by measuring LED voltage and LEDjunction temperature for a range of LED currents and identifying arelationship between the LED voltage and LED junction temperature. 9.The method of claim 5, wherein a relationship between average LEDjunction temperature and the temperature at said given point on thedistal tip is pre-determined by measuring average LED junctiontemperature and the temperature at a given point on the distal tip for arange of LED currents and identifying a relationship between the averageLED junction temperature and the temperature at the given point.
 10. Amethod for determining a temperature in an endoscope, wherein saidendoscope comprises a plurality of viewing elements located in a distaltip of the endoscope and wherein each of said viewing elements comprisesan image sensor having a field of view illuminated by one or more LEDilluminators, said method comprising: measuring a voltage across atleast one of said LED illuminators; and computing a junction temperaturefor the at least one of said LED illuminators by using a value of themeasured voltage and a function representing a relationship between LEDvoltage and LED junction temperature for the at least one of said LEDilluminators, wherein the function representing the relationship betweenLED voltage and LED junction temperature is pre-determined by measuringLED voltage and LED junction temperature for a range of LED currents andidentifying a relationship between the LED voltage and LED junctiontemperature.